JPH03200088A - Method and device for detecting the presence of a moving object - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a position detection method and apparatus capable of detecting the positions and velocities of a plurality of moving objects.

[Prior Art] Conventionally, ultrasonic type and loop type vehicle detectors have been used as means for measuring traffic volume in traffic control systems. However, these vehicle detectors originally exist (
It is a position sensing type, and the speed of individual vehicles cannot be measured with a single sensor.

In order to solve these problems, Sumitomo Electric No. 114, published in 1972, introduced the so-called Doppler effect, in which when radio waves or sound waves are reflected by a moving object, they undergo a frequency shift proportional to the speed of the moving object. A moving object position detection device was proposed.

With this proposal, the number of moving objects (vehicles), speed, and three types of traffic flow parameters can be measured simultaneously and at the same point, and by using a microcomputer in the logic operation section, the device can be extremely versatile. Although it has become possible to have a high and compact configuration, this device cannot detect stopped vehicles in principle because it uses the Doppler effect, and there are problems with the accuracy of detecting the number of vehicles during traffic congestion.

In order to solve this problem, a vehicle presence detection device with a vehicle speed measurement function was devised that uses the level of reflected waves from the vehicle (hereinafter referred to as the "existing wave level") to detect the presence (or stoppage) of a vehicle.

[Problem to be solved by the invention]

However, in order to measure the vehicle speed with this type of conventional presence detection device, it is necessary to install the transmitting and receiving antennas at an angle of inclination of 45° to 70° with respect to the direction of vehicle movement, as shown in Figure 4 (A). However, in terms of vehicle resolution, it is inferior to ultrasonic sensors, and there are also problems with the accuracy of detecting the number of vehicles during traffic jams. This point will be explained in detail.

While a large vehicle such as a bus as shown in FIG. 4(A) exists in the sensing area, the signal level of the microwave received by the presence detection device has a waveform as shown in FIG. 5(A).

Furthermore, as shown in Fig. 4(B), the microwave signal level when two small vehicles are present in the sensing area is the fifth.
The waveform is shown in Figure (B).

When the distance between two small vehicles is small, the position detection device receives the microwaves reflected by the two vehicles.
The valley portion of the waveform in FIG. 5(B) may become thicker than the vehicle detection level.

In such a case, the presence detection device cannot identify the presence of two vehicles from the received microwave signal waveform.

In addition, if the surface of the vehicle is close to a flat surface like a bus, it is not possible to receive a reflected wave with a stable level.Conventional devices first detect the presence of a vehicle, taking into account the detection cracks caused by this signal level drop. The vehicle's presence is sensed for a certain period of time. With this holding time T, vehicle sensing is held for a certain vehicle moving distance (t, o). This moving distance is defined as the vehicle length maintained.

In order to prevent sensing cracks for large vehicles, the vehicle length is set to 3 to 4 m. Therefore, if the distance between two vehicles is 3 to 4 meters or less, it will not be possible to separate and identify the vehicles.

SUMMARY OF THE INVENTION In view of the above-mentioned points, an object of the present invention is to provide a vehicle presence detection method and apparatus that improve the performance of separating and identifying a plurality of moving objects.

[Means for Solving the Problem] In order to achieve such an object, the present invention detects that a moving object to be detected is within a sensing area by detecting that the signal level of the existing wave is higher than the signal level. The existence of the wave is sensed, and while the sensing is being performed, the velocity is continuously calculated by measuring the deviation of the frequency of the Doppler liquid. Using this measured velocity, the signal level of the existing wave is determined to be the signal level. The moving distance of the moving object (this is called the total vehicle length) in the above case is calculated. Further, the signal level of the existing wave is detected as a section and the number of sections where the signal level of the existing wave is equal to or higher than a second specified level which is larger than (or may be equal to) the first level, and using the measurement speed, The separation vehicle length indicating the distance traveled by the moving object when the signal level is above the second specified level, and the distance of the moving object while the signal level of the existing wave is below the second specified level, which is sandwiched between the sections where the signal level is above the second specified level. The present invention is characterized in that the inter-vehicle distance indicating the moving distance is calculated, the number of moving objects is determined based on the total vehicle length, the distance between the vehicles, and the inter-vehicle distance, and the presence sensing signal level for the number of determinations is as described above.

Further, the present invention is characterized in that the speed level corresponding to the determined number of moving objects is as described above.

c' Effect] The present invention calculates the speed and senses the presence of a vehicle by sensing the presence of a moving object in the conventional manner, and then calculates the second level for separation obtained by comparing the second specified level with the signal level of the existing wave. The distance traveled by the vehicle is calculated from the next signal and the instantaneous and instantaneous vehicle speed obtained separately from this, and from this calculation result, the separated portion of the moving object in the signal waveform of the existing wave is identified. Therefore, by correlating the speed calculation results each time this separated portion is identified, the calculation results can be classified for each moving object. Further, since the velocity calculation interval is set to the interval in which the presence of a moving object is being sensed, the number of velocity measurement points will not decrease, and the accuracy of velocity measurement will not be impaired. In addition, if noise removal is performed separately when sensing the presence of a moving object and when separating the moving object, it is possible to not only improve the accuracy of presence sensing and separation performance of moving objects due to noise removal, but also improve the accuracy of presence sensing and separation of moving objects. Mutual influence due to separation can be eliminated.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows the basic configuration of an embodiment of the present invention.

In FIG. 1, reference numeral 100 denotes a speed measuring means for a moving object that measures the instantaneous speed of the moving object by measuring the frequency shift of Doppler waves.

200 is a moving object presence detection device that detects the signal level of the existing wave, and the signal level of the existing wave is set to 1.
The signal level for detecting the presence of the moving object is greater than the signal level for sensing the presence of the moving object, and the signal level for the existing wave is the first comparing means. In addition, the first comparison means uses TOI to reduce malfunctions caused by unnecessary noise.

It also has THI time monitoring means.

As shown in the timing chart of the embodiment of the present invention in FIG. 2, this is an on-delay (T, l) and off-delay (TH,) circuit for the sensing signal 1, and is processed to remove unnecessary sensing cracks. be done.

300 indicates the signal level of the existing wave, a second specified level greater than the signal level for separating the one or more moving objects, and a second specified level for sensing the presence of the one or more moving objects. The signal level of the existing wave is greater than the second comparison means. The second comparison means also includes time monitoring means for TD2 and TH2 in order to reduce malfunctions caused by unnecessary noise. This is the same process as TOI and THI in the first comparison means.

350 is the instantaneous velocity value measured at 100 and 200°3
From the sensing signal output and separation signal output of 00, the sensing signal 2
This is a vehicle length and inter-vehicle distance measuring means that measures the vehicle length and inter-vehicle distance of the separation signal.

400 is the sensing signal of the first comparison means, the separation signal of the second comparison means, and the vehicle length of the sensing signal 2 separation signal.

The presence sensing determining means determines the number of moving objects from the measured value of the inter-vehicle distance, and outputs presence sensing output and speed level corresponding to the determined number of objects.

Next, the process related to vehicle identification in the presence sensing and determining means 400 will be explained with reference to the flowchart of FIG. 3(A).

When the power is turned on, the control procedure shown in FIG. 3(A) is started (step SIO). First, variables 1, TL, LS, and BL used in this control procedure are initially set to O''. Variable ■ indicates the number of times the separated vehicle length is measured. Variables TL, B
L and L indicate the total vehicle length, two-minute vehicle length, and inter-vehicle distance, respectively. Note that, in terms of measurement logic, the separation vehicle length is measured once and the inter-vehicle distance is measured (l-1) times for each secondary signal for sensing.

Next, the presence sensing determination unit monitors the level state of the secondary sensing signal 52 and waits for the level to be on, that is, for the vehicle to enter the sensing area (steps S20→S30→
SIO→520).

When the level of the secondary sensing signal 52 is turned on (see Figure 2), the speed signal from the speed measuring section is accepted, and the secondary sensing signal 52 is turned off (see Figure 2). ), the vehicle speed and all vehicle slots are measured (step S40 process...ΔL is the product of the current speed measurement value and the elapsed time between the previous speed measurement and the current speed measurement).

If there is only one vehicle, after sequentially detecting the separation secondary signal 62 and the obstruction sensing secondary signal 52, presence sensing determination processing (S31), presence sensing signal speed signal The output processing (S32) is performed to prepare for the next vehicle measurement (steps S30→S31→S32→510).

If there are two or more vehicles within the sensing area, the inter-vehicle distance is measured from when the level of the secondary separation signal 62 becomes "°off" until it becomes "on" (step S
72 copies processed).

When the rise of the level "on" of the secondary signal for separation 62 is detected, the value of the variable I is updated, and thereafter the length of the separated vehicle when the secondary signal for separation is at the level "on" is measured. (Step S61 processing).

After repeating and executing the above-mentioned procedure to measure the vehicle length, separated vehicle length, and inter-vehicle distance, the next time Prepare for measurement.

As described above, in this embodiment, since a level for vehicle separation is provided that is higher than a level for sensing the presence of a vehicle, it is possible to reliably separate vehicles. In addition, speed can be measured continuously while the presence of a vehicle is being sensed, and the measurement results can be classified based on the vehicle separation results.
It is possible to measure the presence of a vehicle almost the same number of times as with conventional devices, without compromising measurement accuracy. In addition, if there is only one noise removal circuit for presence detection, increasing the time constant of noise removal in order to improve the precision for presence detection will reduce the separation discrimination performance, but in this example, the separation and discrimination performance is reduced. Equipped with a noise reduction circuit suitable for each purpose,
The mutual influence between presence sensing and separation can be eliminated.

In addition to this example, the following examples can be given.

(1) In this embodiment, when the sensing secondary signal 52 is at the level "on" and the separating secondary signal 62 is turned from the level "off" to "on", multiple vehicles can move into the sensing area. However, if the microcomputer 21 determines whether the following conditions are satisfied, the accuracy of vehicle separation will be further improved.

In this case, as shown in Fig. 3 (B), the input timing of the secondary signal for separation is measured and memorized by a timer, and the measurement results obtained chronologically by the microcomputer are transferred to the vehicle according to the timing. Classify by.

(a) The pulse length (total vehicle length) of the secondary sensing signal 52 is greater than a predetermined setting value.

(b) The pulse interval (inter-vehicle distance) of the secondary separation signal 62 is larger than a predetermined setting value.

(C) Each pulse length of the secondary signal 62 for separation (separation vehicle length)
is larger than a predetermined setting value.

(2) In this embodiment, separation processing for two vehicles has been explained, but the number of separated vehicles may be two or more, and the maximum number of separated vehicles is determined by the size of the sensing area, the length of the vehicle, the noise removal time, etc. Depending on the situation, the room may be adjusted accordingly.

(3) Although microwaves are used for speed detection in this embodiment, it goes without saying that waves having a Doppler effect such as ultrasonic waves may also be used.

〔Effect of the invention〕

As explained above, according to the present invention, even if there are multiple moving objects within the sensing area, the waveform of the existing wave can be separated for each moving object with high accuracy, so the measurement speed can be reduced. In addition to classification, it is possible to identify the number of moving objects, and it is possible to measure traffic volume during congestion, which was impossible with conventional devices.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the basic configuration of an embodiment of the present invention, FIG. 2 is an explanatory diagram showing signal waveforms in the circuit of FIG. 1, and FIG. 3 (A) shows the operating procedure of the embodiment of the present invention. Flowchart, FIG. 3(B) is a flowchart showing the control procedure of the microcomputer in the second embodiment of the present invention, FIG. 4(A)
) and (B) are explanatory diagrams showing the sensing area of the conventional example, and FIGS. 5(A) and (B) are explanatory diagrams showing the vehicle length determination section of the conventional example. 100... Speed measuring means, 200... First comparing means, 300... Second comparing means, 350... Vehicle length, inter-vehicle distance measuring means, 400... Presence sensing determining means.

Claims (1)

[Claims] 1) The presence of a vehicle is detected from the presence wave indicating the signal level of the reflected wave from the vehicle, and the Doppler wave indicating the frequency deviation of the reflected wave from the vehicle is measured. A method for detecting the presence of a moving object that measures the presence and speed of a moving object, the method comprising detecting that one or more of the moving objects is present within a sensing region by detecting that the signal level of the existing wave is equal to or higher than a first specified level. continuously calculate the speed while the sensing is being carried out, and calculate the section and number of waves in which the signal level of the existing waves reaches a second specified level higher than the first level. The separating portion of each of the moving objects in the signal waveform of the existing wave is identified by detection, and the results of the velocity calculation are classified for each of the moving objects in correspondence with the identification result. A method for detecting the presence of moving objects. 2) A moving object presence detection device that detects the presence of a vehicle from the level of a presence wave, the signal level of the presence wave being compared with a first prescribed level for sensing the presence of one or more of the moving objects. and a first comparing means for outputting a sensing signal when the signal level of the existing wave is higher than the first specified level; and while the sensing signal is output from the first comparing means, the Doppler frequency deviation is speed measuring means that continuously calculates the speed; and comparing the signal level of the existing wave with a second specified level higher than the first specified level for separating the one or more moving objects; a second comparing means for outputting a separation signal when the signal level of the existing wave is higher than the second specified level; and a sensing signal and a separation signal based on the sensing signal, the separation signal, and the speed calculated by the speed measuring means The number of moving objects is determined from the calculated vehicle length and vehicle distance, the vehicle speed corresponding to this number of individual vehicles is determined, and the moving object is determined. A presence detection device characterized by comprising presence detection determination means for outputting presence detection signals and vehicle speeds for the number of vehicles.